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Most common sources of intracranial metastasis
Lung cancer
Breast cancer
Skin cancer (melanoma)
Kidney cancer
GI tract cancer
10–15% of brain metastases are of unknown primary source
Most common metastatic carcinomas to the leptomeninges are breast, lung, lymphomas, and leukemia
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Laboratory and radiology studies are the same as for primary neoplasms
Lumbar puncture is needed only if carcinomatous meningitis is suspected
Elevated cerebrospinal fluid pressure, pleocytosis, increased protein levels, and decreased glucose concentration are seen
Malignant cells may be found on cytology
In leptomeningeal metastases, CT scans show contrast enhancement in the basal cisterns or hydrocephalus without any evidence of mass lesions
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A single cerebral metastasis may be irradiated, sometimes following surgical excision
Leptomeningeal metastases receive irradiation and intrathecal methotrexate
For multiple cerebral metastases or widespread systemic disease, the prognosis is poor
Stereotactic radiosurgery, whole-brain radiotherapy, or both, sometimes helps
Memantine
Dosage: 5 mg orally once daily titrated up by 5-mg daily increments every week to 10 mg orally twice daily
In a randomized trial, memantine use prior to and during whole-brain radiotherapy reduced its cognitive toxicity and is therefore recommended
This effect can be augmented through intensity modulated radiation therapy with hippocampal avoidance
Otherwise, palliative care